Electric wires and cables with such contact elements, which exist in numerous forms as cable lugs, receptacles, or clamps, are used in different apparatuses and systems. Such contact elements allow a reliable and detachable electric connection to be quickly established. The advantage of crimp connections is that wires can be connected to the contact element using machines, resulting in a sufficiently stable, conductive connection between wire and contact element.
Efforts have continued to be made, however, to improve the connection between the electric conductor and the contact element concerning its electric and thermal conductivity, pull-off strength, service life, and resistance to corrosion so that it can withstand the effects of impacts, temperature fluctuations, moisture, corrosive atmospheres, or other extreme conditions. This would allow such connections to be used in new applications and make their operation in existing applications more reliable.
Thus, with conventional contact elements, there are depressions on the inside of the crimp section, which is in tight contact with the wire or wire bundle after crimping. The wire is deformed during crimping and pressure is applied to the depressions, providing improved mechanical attachment. At the same time, corrosion layers and lacquer-type insulating material is removed from certain areas thus deformed of the wire surface. In most conventional contact elements, these depressions are grooves running perpendicularly to the longitudinal axis of the wire. With the webs between the grooves, crimping produces a plurality of annular channels on the wire. Thus, after crimping, the wire has a smaller diameter in the area of the annular channels and the risk of the wire being broken increases, which is obviously undesirable.
As described in U.S. Pat. No. 3,892,459, as many as possible small depressions are provided on the inside of the crimp section in other contact elements to obtain as large a contact surface as possible. This, however, has the undesirable result that the small depressions on the side walls of the crimp section are closed due to the deformation of the side walls before the wires can be pressed into the depressions. U.S. Pat. No. 3,892,459 therefore describes that small, approximately square depressions may be provided on the bottom of the crimp section, which is only slightly or not at all deformed during crimping, and larger longitudinal depressions be provided on the side walls. The longer dimension of these longitudinal depressions extends perpendicularly to the longitudinal axis of the wire. Thus also in this case annular channels are formed on the wire, resulting in the aforementioned weakening of the wire and an increase in the risk of wire breakage.
U.S. Pat. No. 3,989,339 describes another conventional crimped connection using oblique channels and ribs.
Advantages of the invention
Upon crimping, each web between the grooves or each rib on the inner surface of the crimp section leaves a helical groove on the wire. Thus the cross section of the wire is reduced uniformly in comparison with the annular grooves in each longitudinal position located in the crimp section as compared to the conventional arrangement. The contact surface between contact element and wire is, however, much greater than that of the conventional contact element. This contact surface between contact element and wire can also be further increased by increasing the number of grooves and ribs, thus reducing the risk of breakage compared to the known crimp connections between contact element and conductor. With the increase in the contact surface, the electric and thermal conductance and, in particular, the mechanical strength are improved due to the crosswise arrangement of ribs and grooves. A preferable distribution of the reduction in the conductor's diameter is achieved when the grooves and ribs are arranged obliquely or helically in parallel to one another.